Bulk-like first-order magnetoelastic transition in FeRh particles

Near-equiatomic, chemically-ordered iron-rhodium (FeRh) alloy is a fundamentally interesting material that may become useful in niche applications making use of its unique magneto functional phenomena, for example, the giant inverse magnetocaloric effect near room temperature that is associated with a sharp first-order magnetic phase transition. The nearly discontinuous antiferromagnetic-ferromagnetic phase transformation in bulk FeRh is well-known; however, the transition broadens considerably in fine particles and films with thickness less than 50 nm, precluding their potential applications. Here, we report an abrupt, bulk-like first-order magnetoelastic transformation in powders consisting of sub-micron particles of nearly equiatomic FeRh compound synthesized via solid-state mechanochemical co-reduction of FeF2 and RhCl3 and subsequent heat treatments. We demonstrate that annealing at temperatures ranging from 600 degrees C to 800 degrees C enables tailoring phase content, particle size, and magnetic properties of the powders. A maximum magnetic-field-induced entropy change of similar to 10 J/kg K at mu(0)Delta H = 1 T has been achieved in powders annealed at 800 degrees C. The retention of extraordinary responsiveness in sub-micron particles of FeRh is likely to open doors for system component fabrication using additive manufacturing methods, along with new opportunities to employ FeRh in theranostics. (C) 2022 Published by Elsevier B.V.

Automated summary

Sub-micron particles of FeRh powder synthesized via solid-state mechanochemical co-reduction exhibit an abrupt, bulk-like first-order magnetoelastic transformation, and the phase content, particle size, and magnetic properties of the powder can be tuned through heat treatments.